High-frequency multiplex signaling system



July 29 1924.

L. ESPENSCHIED HIGH FREQUENCY HULTIPL SIGNALING SYSTEM Original FiledSea. 30 )919 mmtoz Patented July 29, 1924.

UNITED STATES PATENT OFFICE.

LLOYD E SPENSQHIED, OF QUEENS, NEW YORK, ASSIGNOR TO AMERICAN TELEPHONEAND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

HIGH-FREQUENCY MULTIPLEX SIGNALING SYSTEM.

original application filed September so, 1919, Serial No. 327,500.Divided and. this application filed 1 m 16, 1921. Serial No. 461,969.

T0 on whom it may concern:

Be it known that I, Lnoro ESPENSGHIED, residing at Queens, in the countyof Queens and State of New York, have invented certain Improvements inHigh-Frequency Multiplex Signalin Systems, of which the following is aspecification.

This invention relates to high frequency multiplex signaling systems,and particularly to a terminal circuit arrangement embodying the use ofa common translating circuit adapted both to modulate transmittedtelegraph impulses and to demodulate the received high frequency telegraph signals.

This application is a division of my copending application, Serial No.327,500, filed Sept. 30, 1919, entitled High frequency multiplexsignaling systems.

In multiplex signaling systems heretofore used employing a plurality ofcarrier currents of various frequencies, it has been customary to insertin the transmitting and the receivin branches of the terminal circuitatransfiting device individual to each of the said branches. It is theprimary object of the present invention to adapt the terminal circuitarrangement so that the process of modulation, demodulation andamplification of the. various currents in both the transmitting andreceiving branches of the terminal circuit may be performed by a singletranslating circuit. Although the preferable form of translating deviceis a single thermionic vacuum tube or a pluralit of such tubes incombination adapted to 110- tion as a single unit with respect to thetwo branches of the terminal circuit, any well known ty e of translatingdevice, such as, for exampqe, the mechanical repeater, may be used.

Another object of this invention is to provide a circuit arrangementwhereby low frequency telegraph signals or signaling impulses receivedover one line circuit may modulate high frequency oscillations from asource connected with the translating circuit, and the modulated highfrequency oscillations may be impressed upon the transmission linecircuit; and to provide for the demodulation of the high frequencysignals received over the said transmission line a and impressed uponthe same translating circuit. This invention also provides in rangementshown in Fig. 1. and Fig. 2 shows a type of feedback oscillator adaptedto be used with the general circuit shown in Fig ure 1.

Figure 1 shows a means for a plying this invention to the transmission 0telegraphic signals over wires and Fig. 1" shows means for transmissionby radio signalin system. In the figure, L represents a me over whichlow frequency telegraphic signals may be transmitted to the terminalcircuit. This line is connected with the windings of a balanced relaylit having associated therewith a network N adapted to balance the lineL The armature of the relay 1 is adapted to impress impulses of oppositepolarity upon. the input circuit 2; which is ridged across a condenserconnected into the common conductor of the input side of a duplextranslating device. Connected also with the same common conductor,either directly or inductively as shown inthe drawing, is as'oui'ce ofoscillations of carrier frequency G. Across the input side of the saidtranslating device is a transformer '1 for impressing hi h frequencyreceived oscillations upon t 1e said device. Con- 'nect-ed with thecommon terminal of the output side of the device MD .is the outputcircuit 3, by means of which the modulated oscillations may be im ressedby the triple winding transformer upon the transmission line or antenna.A network N is associated with the said transformer to balance eitherthe transmission line ML or the antenna of Fig.1. Bridged across the outat side of the translating device MD is a iffere-n'tial relay R, thearmature of which is adapted t'\ respond to the received impulses andope; and close the low frequency circuit L The relay R, is so designedthat if the network N balances the line L,, the impulses transmittedover the line L by the operation of the armature 4 will cause nodisturbance of the armature 1 1n the output side of the relay.

In the operation of this circuit low frequency telegraphic signalstransmitted o er the line L, will cause the operation of the armature 1and will apply impulses to the circuit 2 which is bridged across theterminals of the condenser K Simultaneous with the impression of the lowfrequency signaling impulses on the condenser K, high frequency carrieroscillatlons from the source G will likewise be impressed across theinput side of the modulating and demodulating circuit MD,. The highfrequency carrier oscillations will be modulated by the impulsesimpressed upon the condenser K and the modulated oscillations which apear in the output side of the modulatlon an d demodulation circuit willbe impressed by the transformer T, upon the output circuit 3 from whichthey will pass to the transmission line ML. Since the low frequencyimpulses and the high frequency carrier oscillations are impressed uponthe common conductor of the balanced modulation and demodulationcircuit, the currents resulting therefrom will flow in oppositedirections through each half of the winding of the relay R in the out utside of the circuit and will cause no e ect upon the said relay. Whenhigh frequency oscillations modulated by telegraphic impulses arereceived over the transmission line ML, they will be impressed by thetransformer T upon the receiving circuit 5 and will pass to the circuit6 tuned to reception frequency. These modulated high frequencyoscillations which are impressed across the input side of'the modulationand demodulation circuit will be demodulated y means of carrierfrequency oscillations impressed upon the same circuit by the source G.The resultant impulses arising from demodulation will operatet-he relayR and accordingly corresponding signals will be impressed upon the lowfrequency signaling circuit L Since the modulated high frequencyoscillations arriving through the circuit 5 are impressed across theinput side of the modulation and demodulation circuit, the impulsesresulting from detection will produce no effect upon the circuit 3 whichis coupled by means of the transformer T with the common-conductor inthe output side of the modulation and demodulation circuit.

Figure 2 shows a novel form of generator of high frequency oscillationswhich is adaptedto be used with the general circuit shown. in Figure 1.In the arrangement shown in- Figure 2 high frequenc oscillatronsarriving over circuit 5 wi be impressed upon the circuit 6 tuned torecaption frequency b the transformer T,. This circuit is tuned y meansof the inductance of one of the windings of the transformer T and by thecapacity of the condenser P1,. The inductance is divided between thegrid and the plate circuitsso as to form the feed back connectionnecessary in an oscillation circuit. The hi h frequency oscillations setup by the oscilation generator Gr will be impressed upon the input sideof the modulation and demodulation circuit as were the oscillations setup by the generator G shown in Figure 1. By means of the oscillationgenerator shown in Figure 2 substantial identity of he uency is obtainedwhich insures good qua ity in the modulation and the detection ofsignals.

Although this invention has been described as being embodied in specificform and arrangement of parts, it is to be under-- stood that it iscapable of embodiment in other and different forms Without departingfrom the spirit and the scope of the patent claims.

What is claimed is:

1. In a signaling system, the combination with a signaling circuit of atransmission circuit, networks individual to and adapted to balance thesaid circuits, a four-wire connecting circuit, a balanced relay adaptedto respond to telegraphic impulses transmitted over the said signalincircuit, a translating circuit common to tie transmitting and receivingpaths of the said fourwire circuit having means to impress thereonimpulses from the said relay, a source of high frequency carrieroscillations and means to modulate the high frequency carrieroscillations in accordance with the telegraphic impulses.

2. In a signaling system, the combination with a low frequency signalingcircuit of a high frequency signaling circuit, a fourwire connectingcircuit, a balanced relay responsive to low frequency signals from saidfirst mentionedsignaling circuit and adapted to impress them upon thesaid four-wire circuit, a source of carrier frequency oscillations alsoconnected with the said four-wire circuit, means for modulating the saidcarrier oscillations by the said telegraph signaling impulses, and meansfor impressing the modulated high frequency oscillations up n the saidhigh frequency signaling circuit.

V 3. In a signaling system, the combination. with a low frequencysignaling circuit of a high frequency transmission circuit,ra fourwireconnecting circuit, means responsive to telegraph currents transmittedby the said low frequency circuit to impress correspondmg impulses uponthe-said four-wire circuit, a source of carrier-current, means toimpress high frequency modulated oscillations upon the said four-wirecircuit, and means to modulate the carrier current in accordance withthe telegraph currents and de modulate the modulated high frequencyuscillations by the carrier current, and to trans modulated outputcurrents upon said high frequency transmission circuit, and means forimpressing the received high frequency oscillations upon the said inputside of said translating circuit, means for heating said receivedoscillations and said carrier oscillations, and for impressing theimpulses re- Suiting from beating upon signaling appare- 5 tus connectedwith said low frequency nalin circuit.

5. n a signaling system comprising two line circuits connected by afour-wire circuit characterized by u, circuit common to the transmittingand receiving paths of the said founwire circuit and leaving a source ofcarrier current connected therewith, the

method of transmitting and receivi 7 halo graph signals which consistsin se ecting teiegrraph impulses. selecting modulated high frequencyosciliutions, modulating the carrier rurrent h the said telegraphimpulses, deinodnleting [he said modulated high fre qneney oscillationsby means of the carrier cur-rem, transmitting the resultant currentsfrom modulation and demodulation and preventing singing over thetransmitting and receiving paths of the four-Wire circuit.

tiw in ii translating circuit having e trans luring device associatedtherewith, the combination with means for impressing low frequencycurrents and modulated carrier freuency currents upon the said inputsideof t 1e said translating circuit of a thermionic osciilntor hsi'ing itsin hit side connected. with the input side of t 1e said translatingcircuit and resonant to carrier frequency and a inodulating-demodulstingdevice connected with the output side of the said oscil lator and :1 isoconnected with the input side of the said translating circuit wherebyosciiisiions of carrier frequency may be supplied thereto to bemodulated by the low frequency currents and to demodulate the modulatedhigh frequency currents.

in testimony whereof, I have signed my name to this specification thisth day of Aprih 1921,

LLOYD ESPENSCHIED.

